JP3142396B2 - Composite polyolefin film for print laminate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a heat-fusible material which can be laminated only by heating and pressing without using an adhesive or an organic solvent when laminating with printing paper or the like. The present invention relates to a film for a print laminate.

[0002]

2. Description of the Related Art It is common practice to laminate a film on printed paper for the purpose of protecting a printed portion of a printed art paper or the like, imparting water and oil resistance, and giving gloss. Such processing is generally referred to in the art as print lamination.

Recently, print laminates have been used in organic solvents,
There is known a print laminating film which can be laminated only by thermocompression bonding without using an adhesive (for example, JP-A-56-24161, Japanese Patent Publication No. 2-2411).
issue).

As a general method of thermocompression bonding a film for print lamination to printing paper, for example, Japanese Patent Publication No.
As shown in No. 411, thermocompression bonding is performed with a pair of pinch rolls composed of a heated metal roll and a rubber roll. The printing surface of the printing paper and the thermal adhesive layer surface of the film are overlapped so that they are in contact with each other, and a heated metal roll surface on the film side and a rubber roll surface on the printing paper side have a linear pressure of 50 to 300 kg / c.
and press-fit through a pinch roll pressurized to m. However, since this metal roll surface is pressurized with high pressure,
It is common that inorganic particles contained in paper and the like easily cause abrasion-like defects.

[0005]

However, the above-mentioned prior art is a film for a print laminate in which a heat-fusible resin is laminated on one side of a biaxially oriented polypropylene film, but a cast film which is not stretched is used. -In the case of a print laminating film in which a heat-adhesive resin is laminated on one side as a film, scratches and the like of the used metal roll are transferred during thermocompression bonding, and the surface quality of the laminated printing paper is reduced. There is a disadvantage that the film surface is easily scratched when laminating papers are stacked one on another,
It was not practical.

An object of the present invention is to provide a film for print laminating which solves the above-mentioned problem and which is less likely to transfer a scratch of a metal roll to a cast film and which is excellent in transparency.

[0007]

As a result of intensive studies, the present invention solves the above-mentioned problems by providing a polyolefin-based heat-fusible resin (B) on one surface of a cast film (A layer) containing polypropylene as a main component. Wherein the layer A has a surface gloss of 110% or more and an average refractive index in the range of 1.500 to 1.5080. And

The polypropylene of the present invention (hereinafter abbreviated as PP) is a crystalline polypropylene, and is a homopolymer of propylene or α such as ethylene or butene-1.
-A copolymer obtained by copolymerizing an olefin at a ratio of 5% by weight or less is also included. The intrinsic viscosity [η] of the PP is 1.2.
~ 2.1 dl / g, melt flow index (MF
I) is 5.0 to 20 g / 10 min, and the isotactic index (II) is 95% or more, more preferably 96 to
It is preferable that the content be in the range of 98% because the transfer resistance of scratches on the metal roll is easily improved. In addition, 12 of the PP
The time until the peak of the DSC isothermal crystallization curve at a temperature of 5 ° C is 3 minutes or less, preferably 5 seconds to 1 minute 30 seconds, more preferably 10 seconds to 60 seconds. This is preferable because transfer hardly occurs. The PP has a known additive,
For example, a nucleating agent, an antioxidant, a heat stabilizer, a slipping agent, an antistatic agent, an antiblocking agent, and the like may be contained. In order to make the time to peak of the DSC isothermal crystallization curve at a temperature of 125 ° C. particularly within the range of the present invention, a nucleating agent,
For example, bis (p-benzylidene) sorbitol, bis (p-methylbenzylidene) sorbitol, bis (p-benzylidene) sorbitol
It is preferable to add (ethylbenzylidene) sorbitol, thiodiglycolic acid or anhydride thereof.

The film containing polypropylene as a main component of the present invention is a film containing 75% by weight or more of a polypropylene component. If necessary, a heat-fusible resin used for the composite film of the present invention, or ethylene-α
An olefin copolymer, an ethylene-propylene-block copolymer, or the like may be mixed at less than 25% by weight. When the content of the polypropylene component in the film is less than the above range, the transparency of the film is liable to be lowered and the metal roll flaw is easily transferred, which is not preferable.

The cast film of the present invention refers to a film obtained by melting and extruding a raw material chip to form a sheet, winding it around a metal roll, cooling and solidifying it. It is necessary to add an additive to the film which has been subjected to heat stretching afterwards and oriented to impart lubricity, and this additive generates voids upon stretching, and the drawback of glitter on the surface of the print laminate paper. It is not preferable to remove the lug and the like generated during film formation in the base layer because the transparency tends to be deteriorated by stretching.

The polyolefin heat-fusible resin of the present invention is preferably a polyolefin resin having a melting point in the range of 45 to 110 ° C. More preferably, it is an ethylene copolymer. For example, ethylene-butene-1, ethylene and acrylic acid, methacrylic acid, methyl methacrylate,
(Meth) acrylic acid ester copolymers, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, ethylene-propylene block copolymers and the like can be mentioned.
Particularly, an ethylene-vinyl acetate copolymer and methyl methacrylate are preferred. The heat-fusible resin layer has a melting peak of 4
It is preferable to have two or more points in the range of 5 to 110 ° C.
For this purpose, it is preferable to mix two or more types of ethylene copolymers having different melting points. For example, a combination of an ethylene-vinyl acetate copolymer and ethylene-butene-1, and a combination of methyl methacrylate and an ethylene-propylene block copolymer are exemplified. The heat-fusible resin layer is preferably formed by setting the melting peak at two or more points within a range of 45 to 110 ° C. because the film handling property and the air release property during lamination are improved.

The polyolefin-based heat-fusible resin includes:
Known additives such as an antioxidant, a heat stabilizer, a slipping agent, an antistatic agent, an antiblocking agent, and the like may be contained as long as the properties of the present invention are not impaired.

The heat-fusible polyolefin resin (layer B)
Is not particularly limited, but is preferably 3 to 8 μm.

The surface of the layer B of the present invention is preferably subjected to a corona discharge treatment in the air or in the presence of a carbon dioxide gas or a nitrogen gas so that the surface tension of the layer B is 35 dyne / cm or more.

The glossiness of the surface of the cast film (layer A) containing polypropylene as a main component of the composite film of the present invention is 110% or more, preferably 115% or more. The higher the upper limit of the gloss, the better, but it is up to 125% at present. If the glossiness of the layer A is less than the range of the present invention, the color tone of the printed portion of the printing paper on which the film is laminated becomes undesirably dull.

The average refractive index measured on the surface of the layer A of the composite film of the present invention is in the range of 1.500 to 1.5080. When the average refractive index is less than the range of the present invention, when the film is laminated, scratches on the metal roll are easily transferred, which is not preferable. On the other hand, if the average refractive index exceeds the range of the present invention, the color tone of the printing portion of the printing paper on which the film is laminated tends to be dull, which is not preferable.

As a method for controlling the average refractive index within the range of the present invention, a method for producing the film of the present invention under specific film forming conditions, a method for aging at a temperature of ordinary temperature to 40 ° C., and / or a method for 70 to 120 A method of performing heat treatment at a temperature of ° C. for several seconds can be combined.

The time required to peak the DSC isothermal crystallization curve of the composite film of the present invention at a temperature of 125 ° C. is preferably 3 minutes or less, more preferably 5 seconds to 1 minute 30 seconds, and most preferably 10 seconds. ６０60 seconds. If the time to peak of the DSC isothermal crystallization curve at a temperature of 125 ° C. exceeds the range of the present invention, when the film is laminated,
It is not preferable because scratches on the metal roll are easily transferred.
Further, it is difficult at present to make the time until the peak of the DSC isothermal crystallization curve at a temperature of 125 ° C. less than the range of the present invention, which is not preferable.

The thickness of the composite film of the present invention is not particularly limited, but is preferably 15 to 40 μm.

The method for compounding the composite film of the present invention is not particularly limited.
A method of laminating in a pipe or a mouthpiece, or a method of forming a cast film containing polypropylene as a main component in the scope of the present invention in advance and extruding a heat-fusible resin, and laminating the film. In particular, a method of joining and laminating in a die is preferable.

Next, a method for producing the composite film of the present invention will be described.

First, a chip containing a predetermined PP as a main component and a polyolefin-based heat-adhesive resin chip are supplied to separate extruders, melt-extruded at a temperature of 210 to 240 ° C., and polymers are combined and laminated by a slit die. To form a sheet
The extruded sheet is wound around a metal roll at a temperature of 0 to 80 ° C. to be cooled and solidified. The surface of the polyolefin-based heat-adhesive resin layer of the film is subjected to a corona discharge treatment in air, the ears are removed, and the film is wound. At this time, the flow rate of the polymer extruded from the die is preferably in the range of 130 to 200 cm / min. The ratio of the speed of the extruded sheet (polymer flow speed) to the speed of the metal roll for cooling (draft ratio) is 30 to
50 is preferred. As a method of cooling and solidifying the extruded sheet, the sheet is brought into contact with the metal roll by using the film layer (layer A) mainly composed of PP of the composite film as the cooling metal roll surface. A method of making close contact with compressed air blown out from a slit-shaped nozzle at a point is preferable.

[0023]

The composite film of the present invention uses a specific PP and a specific heat-fusible resin to form a composite film under specific conditions.
By setting the characteristics of the film within the range of the present invention, it is difficult to transfer the scratches of the metal roll during the thermal compression bonding of the film and the printing paper, and the quality of the surface of the obtained laminated printing paper is reduced. Difficult, and when laminating printing paper is stacked,
It is presumed that the effect of making the surface hardly scratched was obtained.

[0024]

The characteristic values of the present invention are measured by the following measuring methods.

(1) Isothermal crystallization curve of DSC A 10 mg sample was measured at a heating rate of 320 ° C / min by using a DSC (differential scanning calorimeter) type II manufactured by Peak Kinelmer Co., Ltd. ℃, hold for 5 minutes, then cool at the same speed,
Take an isothermal crystallization curve at 125 ° C. The peak refers to the inflection point of this curve. The time to peak means the time from the point when the sample reaches 125 ° C. in the cooling process to the point of inflection at the peak.

(2) Isotactic index (I
I) Vacuum dry the sample at 130 ° C for 2 hours. From now on weight W
Take a (mg) sample, place in a Soxhlet extractor and extract with boiling n-heptane for 12 hours. Next, the sample is taken out, sufficiently washed with acetone, vacuum-dried at 130 ° C. for 6 hours, and thereafter, the weight W ′ (mg) is measured, and it is determined by the following equation. II (%) = W ′ / W × 100

(3) Average refractive index of film Using an Abbe refractometer, Na-D line as a light source, methyl salicylate as a mounting liquid, and changing the direction of a polarizing plate of an eyepiece lens, a refractive index in a specific direction. Is measured by the total reflection method. The average refractive index is (NX + NY + NZ) / 3
Is calculated.

(4) Gloss (JIS Z8741 Method 2, 60 ° Mirror Gloss) Using a gloss meter (Model VG107, manufactured by Nippon Denshoku Industries Co., Ltd.),
The glossiness at the time of 0 ° reflection was measured and determined.

(5) Fragment transferability of metal roll Using a thermocompression bonding apparatus provided with a 500 mm diameter heated metal roll (drive shaft) and a 500 mm diameter rubber roll equipped with a hydraulic press. The layer B of the composite film is superimposed on the printing surface of the paper printed for the book cover, and the film is formed under the conditions of a metal roll surface temperature of 115 ° C., a linear pressure of 50 kg / cm, and a laminating speed of 20 m / min. Laminate by thermocompression bonding with the surface facing the metal roll. Metal rolls have a width of 10
There are scratches of μm and partially scratches of 100 μm width. The scratch transferability of the metal roll was visually evaluated according to the following rank. Rank ：: No transfer of abrasion is observed. ：: Scratches were slightly transferred, but unclear. Δ: Scratches are clearly transferred. X: Scratches and large scratches are also transferred. The above is a rank in which the surface quality of the laminated paper is maintained as the scratch transfer property of the metal roll.

The present invention will be described with reference to examples.

Examples 1-2, Comparative Examples 1-2 Homo PP (II) containing a crystal nucleating agent having an intrinsic viscosity of 1.7 dl / g
= 96%, MFI = 10 g / 10 min, time to peak for DSC isothermal crystallization at 125 ° C. = 23 seconds, antistatic agent content = 0.1% by weight, organic lubricant content = 0.
15 wt%) chips and ethylene-vinyl acetate copolymer (vinyl acetate content = 14 mol%, MFI = 15 g /
10 minutes, melting point = 93 ° C.) ethylene-butene-1 copolymer (butene-1 content = 15 mol%, MFI = 3.6)
g / 10 min, melting point = 85 ° C.) and 5% by weight of chips (content of organic lubricant = 0.2% by weight) are supplied to separate extruders, melt-extruded at a temperature of 220 ° C., and slit-shaped The respective melts were merged and laminated in the same, and formed into a sheet. At this time, the polymer flow rate of the base lip is 180 cm /
min. The sheet was wound around a casting drum for cooling and cooled and solidified while blowing compressed air from a slit-shaped air nozzle to obtain an unstretched composite film having a film thickness of 25 μm. Subsequently, the surface of the heat-fusible resin layer (layer B) of the composite film was subjected to a corona discharge treatment in air, and the ears were cut off and wound. The wetting tension on the B layer surface was 36 dyne / cm. In addition, a heat-fusible resin layer (B
The thickness of the layer was 7 μm. The temperature of the casting drum at this time was as shown in Table 1, and the characteristics of the obtained film and laminated printing paper were as shown in Table 1. In addition, D of the obtained composite film at a temperature of 125 ° C.
The time to peak for SC isothermal crystallization was 29 seconds.

Comparative Example 3 The PP chip of Example 2 was treated with a homo PP having an intrinsic viscosity of 1.8 dl / g (II = 97%, MFI = 8 g / 10 minutes, 125 ° C.)
(Time until peak of DSC isothermal crystallization at the above temperature = 6 minutes 9 seconds, antistatic agent content = 0.1% by weight, organic lubricant content = 0.15% by weight) An unstretched composite film was obtained in the same manner as in Example 2. 1 of composite film
The time to peak for DSC isothermal crystallization at a temperature of 25 ° C. was 6 minutes and 39 seconds. The properties of the obtained film and laminated printing paper are as shown in Table 1.

[0033]

[Table 1] The printed laminate composite film of the present invention has an average refractive index within the range of the present invention, thereby improving the scratch resistance of the film surface and preventing the metal roll from being scratched by thermal lamination with printing paper. Transfer became difficult (Examples 1 and 2), and the surface of the laminated printing paper became high quality.

However, in Comparative Examples 1 to 3, the glossiness of the film or the average refractive index of the film was out of the range of the present invention, and high-quality laminated printing paper was not obtained.

[0035]

According to the present invention, in a composite film for print laminate, by setting the glossiness and average refractive index of the film within the range of the present invention, a print laminate print paper having a high quality surface can be obtained. Was done.

──────────────────────────────────────────────────続 き Continuation of front page (72) Katsuhiro Tsuchiya 1-5 Sakuracho, Takatsuki-shi, Osaka Toray Gosei Film Co., Ltd. (56) References JP-A-56-24161 (JP, A) JP-A-59 -24669 (JP, A) JP-A-63-149149 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (3)

(57) [Claims] 1. A composite film in which a polyolefin-based heat-fusible resin (layer B) is laminated on one side of a cast film (layer A) containing polypropylene as a main component, and the surface glossiness of the layer A is 110% or more. And the average refractive index is 1.5
A composite polyolefin film for a print laminate, which is in the range of 00 to 1.5080. 2. A composite polyolefin film having a temperature of 125 ° C.
2. The composite polyolefin film for a print laminate according to claim 1, wherein the time until the peak of the DSC isothermal crystallization curve at the above temperature is 3 minutes or less. 3. The composite polyolefin film for print laminate according to claim 1, wherein the polyolefin-based heat-fusible resin is an ethylene-based copolymer and has a melting point in the range of 45 to 110 ° C.